A delivery unit may have a baffle pot, a fuel pump arranged in the baffle pot and a jet suction pump delivering into the baffle pot, the jet suction pump comprising a propulsion jet nozzle with a nozzle opening, a mixing pipe, a suction opening, a suction line connected thereto. The jet suction pump is used to deliver fuel from a fuel container into a baffle pot which is arranged within the fuel container.
It is known that fuel containers have many shapes. With the adaptation of the fuel container to the vehicle, using the available space, fuel containers which are subdivided into a plurality of chambers are produced.
These chambers are for the most part connected to a saddle. In such fuel containers, the problem arises that, when there is a low level, the fuel can no longer get from one chamber over the saddle into the other chamber. Since usually only one delivery unit is arranged in a fuel container, the fuel located in another chamber cannot reach the delivery unit. In these cases, jet suction pumps are used to feed the fuel present in another region of the fuel container to the delivery unit or to deliver the fuel at least into the chamber or the region in which the delivery unit is located.
Conventional jet suction pumps are arranged at the bottom of the chambers or the regions of the fuel container from which the fuel is to be delivered to the delivery unit. With the arrangement of the suction opening of the jet suction pump at the bottom of the fuel container, the jet suction pump is always in the fuel and is thus always ready to operate. Jet suction pumps of this type are distinguished by good efficiency. The delivery factor, that is the ratio of combined jet to propulsion jet, is at least around 7. The disadvantage in this case is that, with the propulsion line to the jet suction pump and the combined line from the jet suction pump, two lines are required, which have to be laid and fixed in the fuel container.
Furthermore, it is known to use sucking jet suction pumps which are arranged in the region of the delivery unit. From the jet suction pump, a suction line leads in the region from which the fuel is to be delivered. In order to produce the necessary negative pressure in the suction line, the jet suction pump has a specific propulsion jet nozzle. The outlet opening of the propulsion jet nozzle is designed as a slot. As a result of the slot, the propulsion jet fans out after emerging from the propulsion jet nozzle. The fanned out propulsion jet closes the mixing tube, by which means the necessary negative pressure is produced in order to be able to suck in the fuel over the relatively long suction line. As a result, only one line instead of two lines as hitherto has to be laid in the fuel container and to be fixed. The disadvantage with this arrangement is the low delivery factor of the sucking jet suction pump, which is approximately 2. This low delivery factor is caused by the propulsion jet fanning out after leaving the propulsion jet nozzle.
Furthermore, a jet suction pump is known which is arranged with the outlet end of the mixing pipe in a pot, so that the delivery medium in the pot seals off the end of the mixing pipe with respect to the atmosphere. By means of this liquid closure, a negative pressure is produced at the entry to the mixing pipe, which contributes to improving the suction performance. However, it has been shown that, under certain conditions, the suction performance is no longer achieved, which allows it to be concluded that the liquid closure of the outlet of the mixing pipe is not always ensured.
This can be caused, for example, by there being too low a quantity of the delivered liquid in the pot.